Control device for repairing weaving defects in a pneumatic weaving machine

ABSTRACT

Weft threads are presented in measured lengths by a weft preparing device, comprising a continuously operating drawing off device and an intermittently operating storage device. Said lengths are presented to a main blowing nozzle positioned at one end of the weaving shed. A thread detector is provided at a weaving shed end remote from the main blowing nozzle, said detector comprising a pick up which in absence of a weft thread stops the main shaft of the machine. Said pick up controls, apart from the drive of the main shaft of the machine, also the supply of air to the main blowing nozzle, in such a manner that a defect signal delivered by said pick up immediately causes the main blowing nozzle to be shut off. The main machine shaft is connected to a signal transmitter which issues a signal when the main shaft is stationary, said signal effecting the immediate throwing out of a coupling provided between said main shaft and the weft preparing device. The throwing out movement causes the throwing in of a reverse rotation device and of a coupling between said reverse rotation device and the main shaft, which coupling is normally thrown out. Means are provided to throw out again the reverse rotation device and the corresponding coupling after the main shaft has been reversed through an angle corresponding to a complete weaving cycle and to couple again the weft preparing device with the main shaft. Further means are provided to remove the defect causing weaving thread, which has been freed by the reverse rotation, from the weaving shed by means of auxiliary blowing nozzles, to signal said removal and to initiate thereby the postponed launching of the next weft length and to restart the machine.

United States Patent 1 Van Duynhoven et al.

[451 Apr. 23, 1974 CONTROL DEVICE FOR REPAIRING WEAVING DEFECTS IN APNEUMATIC WEAVING MACHINE [75] Inventors: Adrainus Henricus VanDuynhoven;

Geert Jan Vermeulen', both of Deurme, Netherlands [73] Assignee: N.V.Machinefabrik L. Te Strake,

Deurne, Netherlands [22] Filed: Sept. 10, 1973 [21] Appl. No.: 395,430

Related US. Application Data [63] Continuation of Ser. No. 261,408, June9, 1972,

abandoned.

[52] US. Cl. 139/1 E, 139/ 127 P [51] Int. Cl D03d 51/08 [58] Field ofSearch..... 139/1 R, l E, 127 R, 127 P,

[56] References Cited UNITED STATES PATENTS 2,962,056 11/1960 Paul et al139/1 3,661,185 5/1972 Zamat 139/1 Primary Examiner-Henry S. JaudonAttorney, Agent, or Firm-Marshall & Yeasting 57 ABSTRACT Weft threadsare presented in measured lengths by a weft preparing device, comprisinga continuously op erating drawing off device and an intermittentlyoperating storage device. Said lengths are presented'to a weaving shedend remote from the main blowing noz-.

zle, said detector comprising a pick up which in absence of a weftthread stops the main shaft of the machine. Said pick up controls, apartfrom the drive of the main shaft of the machine, also the supply of airto the main blowing nozzle, in such a manner that a defect signaldelivered by said pick up immediately causes the main blowing nozzle tobe shut off. The main machine shaft is connected to a signal transmitterwhich issues a signal when the main shaft is-stationary, said signaleffecting the immediate throwing out of a coupling provided between saidmain shaft and the weft preparing device. The throwing out movementcauses the throwing in of a reverse rotation device and of a couplingbetween said reverse rotation device and the main shaft, which couplingis normally thrown out. Means are provided to throw out again thereverse rotation device and the corresponding coupling after the mainshaft has been reversed through an angle corresponding to a completeweaving cycle and to couple again the'weft preparing device with themain shaft. Further means are provided to remove thedefect causingweaving thread, which has been freed by the reverse rotation, from theweaving shed by means of auxiliary blowing nozzles, to signal saidremoval and to initiate thereby the postponed launching of the next weftlength and to'restart'the machine;

5 Claims, 8 Drawing Figures CONTROL DEVICE FOR REPAIRING WEAVING DEFECTS.IN A PNEUMATIC WEAVING MACHINE This is a continuation of US. Pat.application Ser. No. 261,408 filed June 9, 1972.

BACKGROUND OF THE INVENTION lengths :by a weft preparing device,comprising a continuously operating drawing off device and anintermittently operating storage device, which is coupled with the mainshaft of the machine as are the weaving healds and the .reed. Saidlengths are presented to a main blowing nozzle, positioned at one end ofthe weaving shed, which is intermittently supplied with air to transportsa id lengths in cooperation with a plurality of auxiliary blowingnozzles positioned between the weaving shed ends through the weavingshed in successive weaving cycles. A weft detector provided at theweaving shed end remote from the main blowing nozzle, said detectorcomprising means which in the absenceof a weft threadstops the mainshaft ofthe machine.

Weaving machines of this type are generally known and operateyusingthepossibilities offered by the handling of the weft threads by means of aflowing fluid such as air, at .high speeds and therefore with a largenumber of picks per time unit.

By the term weaving defectit is meant that a weft thread launched by themain blowing nozzle does not reach the opposite weaving shed end withina predetermined time interval. German Offenlegungsschrift Pat. No.1,904,584 teaches to stop the machine in case of a weaving defect beforethe weft thread causing the weaving defect can be beaten up by the reed,in order to permit easy removal of said weft thread from the weavingshed after said thread has been cut off.

Withthe relatively high weaving speeds prevailing for the weavingmachines of the type considered, it is practically impossible tostop themain shaft and the relatively heavy mass of the reed and the weavinghealds coupled therewith prior to the completion of the beating upmovement by the reed and prior to the weaving shed having been changed.

SUMMARY OF THE INVENTION The invention aims at providing a controldevice for automatically repairing weaving defects in a weaving machineof the above mentioned type, on the basis that the weft thread whichcaused the weaving defect has already beenbeaten up by the reed and hasbeen bound into thecloth prior to the moment at which the main machineshaft and theparts coupled therewith come to a standstill after thedefect has been detected.

According to theinvention, in a control device of the type :abovereferred to the said detector means con trols, apart from the drive ofthe main shaft of the machine, alsothe supply of air to the main,blowing nozzle, in such a manner that an *error" signal delivered bysaid means immediately causes the main blowing nozzle to be shut off.The main machine shaft is connected toa signal transmitter which issuesa signal when the main shaft is stationary, said signal effecting theimmediate throwingout of a coupling provided between said main shaft andthe weft preparing device: The throwing out movement causes the throwinginof a reverse rotation device and of acouplingbetween said reverserotation device and the main shaft, the latter coupling being normallythrown out. Means are provided to throw out again the reverse rotationdevice and the correspond ing coupling after the main shaft has beenrotated back through an angle corresponding to a complete weaving cycleand to couple again the weft preparing device with the main shaft.Further means are provided to remove the defect causing weaving thread,which has been released by the reverse rotation, from the weaving shedby means of the auxiliary blowing nozzles, to signal said removal and toinitiate thereby the postponed launching of the next weft length and torestart the machine.

Therefore with a weaving cycle of 360 (e.g. corresponding to a completerevolution of the main shaft of the weaving machine) during the first180 of which the weft insertion occurs and in the second 180 of whichthe reed movement and the change of weaving shed take place, if a weftdefect is signalled by the thread detector at the end of the weftinsertion phase, the order to stop the main shaft of the machine isgiven, for example to a brake. Then themain shaft will notimmediately beat a standstill but will still permit the reed to beat up theincorrectly inserted weft length into the cloth and permit the shed toclose(at the 270 position) andthen to re-open (at the 360 position). Inthe last mentioned position with normal operation the launching of thenext weft length would start, but as a consequence of thesaid order thesupply signal forithe transport air, required for said launching, isnotgiven or in any case remains without results. For signalling the removalof the faulty weft length use may be made of a separate, e.g.photo-electric device, the signal of which immediately cancels theblocking of the air supply to the main blowing nozzle, so that the nextweft length is signalled and the correct signalof the normal threaddetection effects the restarting of the machine.

However, preferably for signalling the removal of the faulty weft lengthand therefore the removal of the defect use is made of the. normalthread detector. Thereby, however, a correct signal given by the pick upof the thread detector when the faulty weft length is removed couldoccur, when the main shaft has come to a standstill ata position whichis relatively far. beyond the 360 position and therefore a longway in tothe weft phase of the next weaving cycle, and too late to have thetransport air supply to the main blowing nozzle, necessary for thepostponed launching of the next weft length, take place. However, ithasto be noted in this respect that normallyin a weaving machine of thetype considered a weft length, after it has been beaten up into thecloth, is cut withthe intermediary of a cutting means prior tothe nextlaunching at the position between the mainblowing nozzle and theadjacent cloth edge. Thereby the launching of the next weft iength wouldnot be carried out in spite of the cob rect" signal, while themachinedrive would nevertheless be started by the same correct signal. Saidlast mentioned problem is obviated in a simple and effective manner in apreferred embodiment of the. inven tion, in that the pick up of thethread detector at the same time controls the cutting means so that thecutting means is immediately switched off by the defect signal deliveredby the pick up and is switched on again by the correct signal deliveredby the pick up when the defective weft length is removed.

In this manner the weft thread which has caused the weaving defectremains connected with the next weft length and said last mentioned weftlength is drawn into the weaving shed when the faulty weft length "isremoved. Thereby for launching the next weft length one is not dependenton whether or not the normal transport air supply to the main blowingnozzle has been restored, while the moment at which the main shaft comesto a standstill after the signalling of a weaving defect is not criticalbut may be anywhere within the next weft phase, e.g. 270 after themoment of detectron.

According to a further feature of the invention a gripping device ispositioned at the launching side of the machine adjacent the beating upline, said gripping device being adapted to be operated during a shortinterval by a signal delivered at the end of a reverse rotation movementin order to move a faulty weft length from its beating up position intothe path of the transport jet of the main and auxiliary blowing nozzles.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view of apneumatic weaving machine provided with the control device according tothe present invention.

FIG. 1A is a perspective view of the weaving machine.

FIG. 1B is another perspective view of the weaving machine.

FIG. 2 is a diagrammatic view of the weft preparing device with the mainblowing nozzle and its supply.

FIG. 3 is a diagrammatic perspective view of the discharge end of themain blowing nozzle and of the adjacent parts of the cutting means andthe gripping device.

FIG. 4 is a block diagram showing the pick up of the detector connectedwith the electro-magnetic main coupling, the electro-magnetic device forshutting off the supply of air to the main blowing nozzle and the devicefor switching off the cutting means.

FIG. 5 is a block diagram of a signal transmitter coupled with the mainshaft of the machine, a pulse emitter and the electro-magnetic devicefor throwing out the coupling between the main shaft and the weftpreparing device, and

FIG. 6 is a block diagram of a switch, an electropneumatic device forstarting the reverse rotating device, the device for switching on thecoupling between said lastmentioned device and the main shaft, and thecontrol device for the gripping device With reference to FIG. 1 theweaving machine has been indicated at 1. The main shaft 2 of saidmachine is normally driven through the electro-magnetically controlledcoupling 3 by the main drive motor 4 as shown in FIGS. 1 and 1B, andimparts in a well-known manner (not further shown) during the relativephase of the weaving cycle a reciprocal movement to the reed 5 and an upand down movement tothe weaving healds (5A). The main shaft 2 furtherdrives through an intermediate shaft 2a and a coupling 6 which may beelectro-magnetically thrown out, the input shaft 7 of the weft preparingdevice 8 as shown in FIGS. 1 and At one side of themachine 1, i.e., theright side as seen in FIG. 1, in front of the opening of the weavingshed the main blowing nozzle 9 is positioned, by means of which duringnormal operation a weft length 10 prepared by the weft preparing device8 is transported through the weaving shed in cooperation with aplurality of auxiliary blowing nozzles 11 carried by the reed 5. Thelaunching of a prepared weft length is effected in a well-known manner(see FIG. 2) each time when; due to the diaphragm 12a of the so-calledquick air release means 12 being switched over into the positionindicated with broken lines), a sudden and brief connection is effectedbetween the main blowing nozzle 9 and the reservoir 13. In the latterreservoir a measured quantity of air has been accumulated during thepreceding period, supplied via a valve 15, controlled by a cam 14associated with the weft preparing device, and via the quick airreleasemeans 12. FIG. 2 shows the weft preparing device in that phase ofa normal weaving cycle in which the quick air release means 12 isconnected through the valve 15 and the conduit 16 with the air supplyconduit 17, the reservoir 13 is being filled through the quick airrelease means, and the connection between the main blowing nozzle 9 andthe reservoir 13 is closed by the diaphragm 12a, while the buffer device18 is preparing a fresh weft length 10 in loop shape from the weft yarncontinuously supplied from the drawing off rollers 19. The launching ofsaid last mentioned weft length is effected as soon as the thread clamp21 is opened and the valve 15 is placed by the cam 14 against thepressure of the spring 20 in a position in which the conduit 16 isconnected with the air release conduit 22 whereby the diaphragm l2a isswitched in the above described manner and as a result thereof air fromthe reservoir 13 is supplied to the main blowing nozzle 9. The shafts 7aand 7b of the cam 14 and the drawing off rollers respectively, as wellas the actuating shaft (not further shown) of the thread clamp 21receive their motion from the input shaft 7 of the weft preparing device8.

Adjacent the discharge opening of the main blowing nozzle 9 there is theusual cutting means 23 (see FIG. 3) which in the embodiment showncomprises a fixed cutting blade 23a, rigidly mounted to the machineframe 25 through a sleeve 24, and a movable cutting blade 23b which issecured to a shaft 26 rotatably jour-.

nalled in the sleeve 24, the movable blade being axially pulled towardsthe fixed blade by a spring (not shown) received in the sleeve 24. Anarm 27 is fixed to the shaft 26 and is pivotally connected-to anactuating rod 28 in which is reciprocable the direction of the arrow toactuate the movable knife 23b. Normally a weft length after beinginserted and beaten up by the reed into the cloth is cut by said cuttingmeans 23. The cutting means 23 may, however, be made inoperative bymoving the movable cutting blade 23b with the intermediary of a push rodor plunger 29, coaxial units the. shaft 26, against the action of thespring in the sleeve 24, so that it is moved away from the fixedblade23a and the turning movement (which continues normally) is nolonger effective. For this purpose the push rod 29 is connected with anelectro-magnetically energizable actuating device which may be of theelectropneumatic or electro-mechanical type and has been indicated at 30rather diagrammatically.

At a short distance from the discharge opening of the main blowingnozzle 9 there is a guiding means 31 which is reciprocable in a planeperpendicular to the axis of the main blowing nozzle 9 (in the directionof the arrow) together with the reed and is adapted to guide, after thelaunching of a weft length by the main blowing nozzle 9, the tail end ofsaid weft length and the head end" 10" of the next weft length,connected therewith, between the cooperating blades 23a and 23b of thecutting means 23 (see the thread portion indicated in FIG. 3 with thedash lines 10', 10"). It appears from FIG. 3 that the next weft lengthis thereby drawn into the slit shaped space of a lateral wing 9a of themain blowing nozzle 9.

A thread clamp 32 is mounted in the lateral wing 9a and comprises aclamping rod 33 movable in the direction of the arrow, said rod beingconnected with one end of a double armed lever 35 pivotable around afixed point 34, said lever being engaged at its other end by a spring 36which tends to keep the clamping rod 33 in its inoperative position. Thespring loaded end of the lever 35 is also connected to anelectro-pneumatic or electro-mechanical actuating devicediagrammatically indicated at 37, which upon energization puts theclamping rod 33 against the action of the spring 36 in its operativeposition, in which the head end 10" may be clamped in the positionindicated in FIG. 3 with broken lines. The thread clamp 32 constitutesone part of a special gripping device, the purpose of which will befurther elucidated hereinafter, a second part of which is constituted byan ejector means 38, which is reciprocable along the selvage and islocated with its operative end adjacent the beating up line x. Areciprocal movement may be imparted to the ejector means 38 by means ofan electro-pneumatic or electromechanical actuating device,diagrammatically shown at 39.

At the side opposite to the main blowing nozzle 9 a thread detector 41is provided in the launching path, within the suction nozzle 40 (FIG.1), e.g. constituted by a photo-electrical pick up with light emitterand light receiver according to U.S.Pat. No. 3,658,098. During normaloperation said thread detector delivers for each weft within apredetermined time interval, e.g. determined by a so-called vaneswitched oscillator (with which the oscillation is determined by theposition of a vane coupled to the main shaft of the machine) within theconsidered weaving cycle a signal which constitutes an indication for anon-faulty weft, which signal keeps the machine in its normal operatingcondition.

However, as soon as the pick up 41 does not observe the presence of aweft length within thepredetermined time interval the said signal is notissued, so that in fact the pick up delivers an error" signal f (see thediagram in FIG. 4). As soon as said error" signal f occurs and thereforea weaving defect is'presentfthe coupling 3 is thrown off through theenergization of the correspond, ing coil s1.- Thereby the main shaft2-is disconnected from the main motor 4 but keeps on moving'forsome timetogether with the reed 5 and the weaving healds connected therewith andis brought to a standstill by a brake (not shown)-in a position between360 and 540, e.g. 270 after the moment of detection.

At the same moment at which the coil s1 is energized a second coil s2 isenergized which is associated with the electro-pneumatic valve 42 (seeFIG. 2) which has been provided in the release conduct 22 and by whichsaid release conduct is then closed so'that the quick release means 12cannot release and the connection between the main blowing nozzle 9 andthe transport air reservoir 13 remains interrupted so that the launchingof the fresh weft length, which has been prepared already and whichshould be launched after the beating up by the reed, does not takeplace. At the same time also the coil s3 of the device 30 is energizedby which the cutting means 23 becomes inoperative and the incorrectlyinserted weft length is not cut at the time of the beating up by thereed or after that time.

The further course of the repair process is as follows:

As soon as the main shaft (at about 270 after the detection) has come toa standstill, e. g. at a position with open weaving shed and retractedreed, a signal transmitter 43 suitable therefor and coupled with themain shaft (see FIG. 1 and 5) emits a signal 44. Said signal controls apulse emitter 45, e.g. a monostable multivibrator, which delivers at itsoutput end a brief pulse 46 for the energization of the coil 54 of theelectro magnet 47 whereby the coupling 6 is uncoupled against the forceof the spring 48 (FIG. 1), so that the weft preparing device 8 isdisconnected from the main shaft of the machine.

The uncoupling of the coupling 6 is attended with the closing of a pairof contacts 49 (e.g. of a reed switch) whereby the energization occursof a coil s5 of the electro'pneumatic switching on valve 50 of apneumatic reverse rotation cylinder 51 and of the switching on coil s6of the electro-magnetic auxiliary coupling 52 which is provided betweenthe main shaft 2 and the reverse rotation cylinder 51.

Therefore the main shaft 2 is reversed directly after it has come to astandstill, by the reverse rotation cylinder 51 through a completerevolution. The end of the reverse rotation movement is governed by thespecial construction of the coupling 6 between the intermediate shaft 2aand the weft preparing device 8. As indicated in FIG. 1 the coupling 6comprises a first disc 6a having a peripheral cam 53 projecting in theaxial direction, and a second disc 6b having a peripheral notch 54corresponding with the cam 53. Due to the fact that the signal whichenergizes the coil s4 of the electromagnetic device 47 for uncouplingsaid coupling only operates briefly, the coupling 6 tends to coupleagain under the influence of the spring 48 shortly after the main shaft2 has come to a standstill. However, said coupling is prevented up tothe moment at which the cam 53 and the notch 54 have re-arrived directlyopposite to each other and this is exactly the moment at which the mainshaft 2 has been reversed by the reverse rotation cylinder 51 through360. At the same time when at that moment the coupling 6 is recoupled,the

contacts 49 are moved apart and therewith the auxili-j ary coupling 52is uncoupled while the electropneumatic switching on valveSOis.againswitched off and the reverse rotationcylinder 51 may return to'itsinitial position under the influence of the return spring 55. i i

Herewith the machine has arrived ina position in which the main shaftand thereby the reed, the weaving healds and the weaving shed are againin the same positions as when the launching of the faulty'weft lengthtook place. However,'the main drive and the coupling 3 remainuncoupledup to the moment at which the faulty weft length has beenremoved from the weaving shed. By the reverse rotation of the main shaft2 the bindingof the faulty weft length in the cloth has been cancelledand therefore said length lies freely in the opened shed. In order nowto further the removal of the thus freed weft length from the weavingshed the above mentioned ejector means 38 is energized so that it gripsthe freed weft length at the beating up line and brings it in line withthe axis of the main blowing nozzle and the auxiliary blowing nozzlescooperating therewith. For the energization of said ejector means use ismade in the embodiment shown of the re-opening of the contacts 49. Thesignal corresponding with said opening is supplied e.g. by an invertingamplifier 56 (see FIG. 6) to a pulse emitter such as the monostablemulti-vibrator 57 which issues a brief signal 58 to the energizationcoils s7 and s8 of the devices 37 and 39 respectively. Thereby theclamping rod 33 is brought in its operative position so that the tailend of the faulty weft length and the head end 10" of the next weftlength still connected thereto are fixed during a short time in theposition indicated in FIG. 3 near the lateral wing 9a of the mainblowing nozzle 9, while the ejecting means 38 grips the tail end 10' ofthe faulty weft length and returns it from the beating up position intothe launching path and immediately thereafter withdraws. The faulty weftlength has thereby arrived under the influence of the auxiliary blowingnozzles 1 1, which are in the retracted position of the reed fullyenergized, and is carried out of the weaving shed by transport jetsissued by said auxiliary blowing nozzles 11. The faulty weft lengthtakes along with it the already completely prepared fresh weft length(which has been released by the clamping rod 33 which in the meantimehas been retracted to its inoperative position). Thereby the pick up 41of the thread detector is passed which therefore observes a correct weftand delivers the signal necessary for the restarting of the normaloperation of the machine. Said signal causes the reconnection of thecoupling 3 with the main motor 4 and from this moment the normaloperation of the machine is restored. The fresh weft length has beenlaunched at this moment and is cut after the beating up of the reed bythe cutting means 23 which has been returned to its normal operativeposition. The faulty weft length is sucked in by the sucking nozzle 40and afterwards it is cut off in a known manner as is done with thenormally woven weft lengths, as a superfluous piece of thread.

We claim:

1. A control device for repairing weaving defects in a weaving machineof the type in which the weft threads are presented in measured lengthsby a weft preparing device comprising a continuously operating drawingoff device and an intermittently operating storage device which iscoupled with the main shaft of the machine as are the weaving healds andthe reed, said lengths being presented to a main blowing nozzlepositioned at one end of the weaving shed, said nozzle beingintermittently supplied with air to transport said lengths incooperation with a plurality of auxiliary blowing nozzles positionedbetween the weaving shed ends in subsequent weaving cycles through theweaving shed, a thread detector being provided at the weaving shed endremote from the main blowing nozzle, said detector comprising a pick upwhich in absence of a weft thread stops the main shaft of the machine,characterized in that said pick up controls, apart from the drive of themain shaft of the machine, also the supply of air to the main blowingnozzle such that a defect signal delivered by said means immediatelycauses the main blowing nozzle to be shut off, whereas the main machineshaft is connected to a signal transmitter which issues a signal whenthe main shaft is stationary, said signal effecting the immediatethrowing out of a coupling provided between said main shaft and the weftpreparing device, the throwing out movement causing the throwing in of areverse rotation device and of a coupling between said reverse rotationdevice and the main shaft, which coupling is normally thrown out, meansbeing provided to throw out again the reverse rotation device and thecorresponding coupling after the main shaft has been reversed through anangle corresponding to a complete weaving cycle and to couple again theweft preparing device with the main shaft, further means being providedto remove the defect causing weaving thread which has been freed by thereverse-rotation, from the weaving shed by means of the auxiliaryblowing nozzles, to signal said removal and to initiate thereby thepostponed launching of the next weft length and to restart the machine.

2. A control device according to claim 1 for a weaving machine providedwith a cutting means which is adapted to cut the weft lengths aftertheir launching, in a point between the main blowing nozzle and theadjacent edge of the fabric, characterized in that the pick up of thedetector at the same time controls the cutting means such that thecutting means is immediately made inoperative by the defect signaldelivered by the pick up and is made operative again by the correctsignal delivered by the pick up when the faulty weft length is removed.I

3. A control device according to claim 1, characterized in that at thelaunching side of the machine, adjacent the beating up line a grippingdevice has been arranged, which is adapted to be made operative for abrief time by a signal delivered at the end of a reverse rotationmovement in order .to place a faulty weft length from its weft positioninto the transport jet path of the main and auxiliary blowing nozzles.

4. A control device according to claim 3, characterized in that thegripper device comprises a thread clamp provided at the dischargeopening of the auxiliary blowing nozzle and an ejector means mountedreciprocally movable along the cloth edge and situated with its forkshaped gripper end adjacent the beating up line.

5. A control device according to claim 4, characterized in that thethread clamp comprises a clamping rod movable up and down in a slitshaped chamber of the lateral wing of the main blowing nozzle.

1. A control device for repairing weaving defects in a weaving machineof the type in which the weft threads are presented in measured lengthsby a weft preparing device comprising a continuously operating drawingoff device and an intermittently operating storage device which iscoupled with the main shaft of the machine as are the weaving healds andthe reed, said lengths being presented to a main blowing nozzlepositioned at one end of the weaving shed, said nozzle beingintermittently supplied with air to transport said lengths - incooperation with a plurality of auxiliary blowing nozzles positionedbetween the weaving shed ends - in subsequent weaving cycles through theweaving shed, a thread detector being provided at the weaving shed endremote from the main blowing nozzle, said detector comprising a pick upwhich in absence of a weft thread stops the main shaft of the machine,characterized in that said pick up controls, apart from the drive of themain shaft of the machine, also the supply of air to the main blowingnozzle such that a defect signal delivered by said means immediatelycauses the main blowing nozzle to be shut off, whereas the main machineshaft is connected to a signal transmitter which issues a signal whenthe main shaft is stationary, said signal effecting the immediatethrowing out of a coupling provided between said main shaft and the weftpreparing device, the throwing out movement causing the throwing in of areverse rotation device and of a coupling between said reverse rotationdevice and the main shaft, which coupling is normally thrown out, meansbeing provided to throw out again the reverse rotation device and thecorresponding coupling after the main shaft has been reversed through anangle corresponding to a complete weaving cycle and to couple again theweft preparing device with the main shaft, further means being providedto remove the defect causing weaving thread which has been freed by thereverse rotation, from the weaving shed by means of the auxiliaryblowing nozzles, to signal said removal and to initiate thereby thepostponed launching of the next weft length and to restart the machine.2. A control device according to claim 1 for a weaving machine providedwith a cutting means which is adapted to cut the weft lengths aftertheir launching, in a point between the main blowing nozzle and theadjacent edge of the fabric, characterized in that the pick up of thedetector at the same time Controls the cutting means such that thecutting means is immediately made inoperative by the defect signaldelivered by the pick up and is made operative again by the''''correct'''' signal delivered by the pick up when the faulty weftlength is removed.
 3. A control device according to claim 1,characterized in that at the launching side of the machine, adjacent thebeating up line a gripping device has been arranged, which is adapted tobe made operative for a brief time by a signal delivered at the end of areverse rotation movement in order to place a faulty weft length fromits weft position into the transport jet path of the main and auxiliaryblowing nozzles.
 4. A control device according to claim 3, characterizedin that the gripper device comprises a thread clamp provided at thedischarge opening of the auxiliary blowing nozzle and an ejector meansmounted reciprocally movable along the cloth edge and situated with itsfork shaped gripper end adjacent the beating up line.
 5. A controldevice according to claim 4, characterized in that the thread clampcomprises a clamping rod movable up and down in a slit shaped chamber ofthe lateral wing of the main blowing nozzle.